SEEDS. 



By John R. Dymond, B.A., Seed Analyst, 

 Dept. of Agriculture, Ottawa. 



Seeds may be studied from two points of view. 

 We may study the use which plants make of seeds 

 cr the use which man makes of them. From man's 

 point of view there are two uses for seeds ( 1 ) as 

 food fcr himself and animals and (2) for the pro- 

 duction of crops. These different points of view are 

 not unrelated and any intelligent discussion of the 

 subject must include a consideration of all three. 



Plants are living organisms: their life, like that 

 of all animals, is limited. Some trees live for thou- 

 sands of years, other for hundreds, but most plants 

 live for only a few years and a very large number 

 grow up from seed, flower, mature their seed and 

 die all in one season. Such plants are called an- 

 nuals and they are common in parts of the world 

 v/ith severe winters like ours. 



One of the uses of the seed to the plant is to 

 preserve its kind through periods of drought, cold 

 cr other conditions that would kill the growing 

 plant. In reality the seed is a very small plant 

 carrying with it a supply of food material. In 

 some ways it is comparable with a bird's egg which 

 is packed with food material to provide for the 

 development of the little chick until it is ready to 

 break the shell and pick up its own living. Similarly 

 a supply of food material is stored in the seed for 

 the support of the little plant until it has established 

 its roots in the soil and leaves in the air and is 

 ready to make its own food from the elements drawn 

 from the soil and the air. 



A plant or animal is most helpless and most easily 

 destroyed when it is young, but nature has provided 

 that, packed away in a seed, the miniature plant is 

 able to withstand very adverse conditions. It may 

 be subjected for long periods to the low tempera- 

 tures of winter wtihout injury and the absence of 

 moisture which kills plants only serves to prolong 

 the life of the seed. The ability to withstand such 

 conditions is what makes it possible for many plants 

 to survive in parts of the world where otherwise 

 ihcy would be killed by cold winters or seasons of 

 Icng continued drought. 



This, however, is not the only function of seeds 

 in plant life. A single plant sometimes produces 

 hundreds of thousands of seeds, by means of which 

 it may produce other plants like itself over a wide 

 area of country. Being so well fortified against 

 injury the little plant in the seed is not nearly so 

 easily killed as a little seedling of the same plant 

 would be. It may be carried long distances and he 



dormant for a considerable time before starting into 

 'ife as a new plant. Some (e.g. thistles and dande- 

 lions) are provided with downy plumes which enable 

 them to flea' in the air and to be carried about by 

 wind. The keys of the maple and basswccd serve 

 the same purpcse. Others have barbed or hooked 

 hairs by which they attach themselves to passing 

 animals (the various burs). Still others are pro- 

 duced in attractive fruits which entice birds and 

 other animals to carry them away as food. Many 

 seeds pass undigested through the digestive tract of 

 animals. Seeds are aften carried long distances by 

 the water in streams, by the wind over the top of 

 snow, in mud attached to the feet of birds and 

 animals and in hundreds of other ways. A plant 

 would not spread its kind over a very wide area 

 if it had to depend on little seedlings being dis- 

 tributed about. 



The ability of the seed to maintain its vitality fcr 

 a number of years is an important factor in the 

 propagation of plants by seeds. It is a common ex- 

 perience for a farmer who has a field containing 

 a certain kind of weed, to seed it to hay or pasture 

 for a number of years, during which he will see 

 few if any of the weeds, and then to plow it up 

 and find plenty of the weeds still in his field. The 

 plants have survived in the field in the form of 

 seeds. 



A consideration of these facts makes us realize 

 what an important part seeds play in the plant's 

 struggle to maintain its kind on the earth in com- 

 petition with other plants and in spite of the adverse 

 conditions which overtake it from time to time. 



All plants, however, do not produce seeds. Ferns, 

 mosses, mushrooms and many other plants are pro- 

 pagated by means of spores. Ages ago all plants 

 living on the earth were reproduced by means of 

 spores. The great forests that produced our coal 

 were not made up of seed plants. The advantage 

 which seed plants have over spore plants in the 

 struggle for existence is seen in the fact that to-day 

 seed plants are the dominant ones of the earth. 



So far we have considered seeds only from the 

 plant's point of view. Man has found them of 

 great use to him as well. We have already seen 

 that the mother plant stores a great deal of food 

 material in the seed for the use of the little plant 

 during the time it is developing its roots and leaves 

 just as the hen's egg is stored with food for the 

 use of the chick during its development. Just as 



